This invention is generally related to my co-pending applications, U.S. Ser. No. 121,672 filed on Nov. 27, 1987 for "IMPROVED FUEL HEATER", still pending, and my "DIESEL FUEL HEATER" Ser. No. 188,304 patent application filed on Apr. 29, 1988, still pending, both of which are incorporated herein by reference.
This invention generally relates to devices that preheat fuel for use in engines, and more particularly, to thermostats for use in these types of fuel heaters.
It is well known that heating fuel prior to its introduction into the combustion chamber of an engine increases the efficiency of the engine. There are many obstacles to overcome when designing a fuel heating device. The primary object of these fuel heaters is to provide the combustion chamber with fuel that is warmed to a predetermined temperature. The heat output of the fuel heater must be adjustable to satisfy the different amounts of fuel needed, depending on whether the truck is idling or accelerating. The fuel heater must also work within a wide range of environmental temperatures and pressures. The heat output required from the fuel heater at warm temperatures is much less than the heat output required when the outside temperature is below zero.
An important characteristic of the fuel heaters of this type is that the fuel heater must be inexpensive to manufacture and relatively easy to install. Savings from this type of device occur over an extended period of time and results from decreased fuel consumption. Additionally, fuel heaters of this type decrease the amount of harmful emissions created by a combustion engine.
The prior art contains a variety of fuel heaters. U.S. Pat. No. 4,146,002 issued to Quinn on Mar. 27, 1979 heats gasoline by passing the gasoline through helically shaped tubing that is surrounded by engine coolant. Similarly, U.S. Pat. No. 4,700,047 issued to Crossett on Oct. 13, 1987 heats diesel fuel by passing the diesel fuel through an elongate heat exchange coil which is enclosed inside a coolant containing housing.
My prior inventions, U.S. Pat. No. 4,367,717 issued on Jan. 11, 1983; my co-pending application Ser. No. 121,672 filed on Nov. 17, 1987 still pending; my patent application Ser. No. 188,304 entitled "DIESEL FUEL HEATER" filed on Apr. 29, 1988 still pending and my co-pending patent application entitled "SPIRAL DISTRIBUTOR FUEL HEATER" Ser. No. 186,939, still pending all include a thermostat to monitor and regulate the heating of the fuel prior to its introduction into the engine's combustion chamber.
The presently available thermostats for these fuel heaters operate by monitoring the temperature of either the fuel or coolant and once the fuel or coolant reaches a predetermined temperature, the flow of the coolant through the heat exchange chamber is blocked until such time as the temperature of the fuel decreases to its predetermined, preferred temperature. At present, the efficiency of these thermostats is decreased whenever the flow rate or pressure of the coolant or fuel fluctuates. These fluctuations may be caused by a defective water pump; fuel pump or even by the sudden acceleration of the engine. Quite often, when the flow rate or pressure of the coolant fluctuates, the thermostat will stick in the open or closed position and the fuel heater will not operate properly. The present invention addresses the problem by being much more sensitive to the overall fluctuations in flow rate and pressure of the coolant or fuel while being less sensitive to the sudden fluctuations in flow rate or pressure.
Additionally, the flow of fuel and coolant in the present invention is arranged so as to flow perpendicularly to the various elements of the thermostat. This overcomes the problem which occurred in some of the prior thermostats wherein a sudden increase in the demand for coolant would draw the needle valve towards the needle valve housing and restrict the flow of coolant in the fuel heater. Another approach has been to direct the coolant inwardly perpendicular to the needle valve. Over a period of time this will cause the needle valve to improperly seat in the needle valve housing and greatly reduce the efficiency of the needle valve.